Adults who suffer a concussion are three times more likely to die by suicide than the rest of the population, according to a new Canadian study that suggests a need for better long-term follow-up for patients.

There was a median delay of six years between the concussion and the suicide, the study found. About half of those who killed themselves had seen a doctor in the last week of their lives.

The study, published in the Canadian Medical Association Journal on Monday, found that people who suffered concussions on weekends tended to fare worse than others. It's not entirely clear why weekend concussions led to a greater suicide risk, but it could be that people who injure themselves outside of the workplace are less likely to seek medical attention, said Dr. Donald Redelmeier, senior author and senior core scientist at Toronto's Institute for Clinical Evaluative Sciences.

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"These are not innocuous things you can shrug off," he said. "There's this machismo image, as if the human brain were perfectly invulnerable just because it's encased in bone."

To conduct the study, researchers analyzed data for all adults diagnosed with a concussion in Ontario from 1992 to 2012. They excluded serious concussions that required a hospital stay. Of the more than 235,000 individuals identified, just over half were men and the mean age was 41.

The study authors followed the individuals for several years following the concussion diagnosis. In total, 667 individuals took their lives, or about 31 deaths for every 100,000 people. That's three times the suicide risk for the general population, which is about nine in 100,000, according to Redelmeier.

Although the study doesn't prove that concussions cause a person to become suicidal, the link is important and shouldn't be ignored, Redelmeier said. Possible explanations for the link could be that some individuals are prone to reckless behaviour that they come to later regret, or it could be that concussions cause long-term brain injuries that lead to increased impulsivity or depression. Another explanation is that people simply don't give themselves enough time to recover following a concussion and experience ongoing frustration and disappointment that they can't get back to "normal."

Dr. Gabriela Ilie, a post-doctoral fellow at Toronto's St. Michael's Hospital who studies traumatic brain injuries, said the new findings should be a wake-up call.

"We shouldn't be surprised at those relationships," she said. "Something has to be done."

Ilie's research has found concussions to be linked to a number of serious problems in young people, including an increased risk of suicide, being victimized by bullies, experiencing anxiety and depression. She argues that professional sports culture continues to glorify violence and underplay the risks of concussion and other brain injuries, which sends the wrong message to young people.

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"It's not okay for us to watch others be injured in the name of sports and entertainment," she said.

The study authors suggest that people who experience a concussion may require long-term follow-up to monitor their psychological state. And individuals must also realize how devastating concussions can be. We often hear about the problem of concussions in NHL players or other professional athletes. But Redelmeier says that people need to realize that injuries suffered while working on a home-improvement project or because of a car accident are just as serious and need medical care, ample recovery time as well as medical follow-up care. The main message is that we all need to take the risks of concussions more seriously, he said.

"If you had an allergic reaction to penicillin 20 years ago, you want to mention that to your doctor," Redelmeier said. "If you had a concussion 15 years ago, you might also want that as part of your medical record."

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